1. Field
The present invention relates to a battery pack management technology, and more particularly, to an apparatus and method for controlling the connection of a plurality of battery packs when connecting the battery packs in parallel.
2. Description of Related Art
Recently, with the active development of storage batteries, robots, satellites, and the like, along with the dramatically increasing demand for portable electronic products such as laptop computers, video cameras, mobile phones, and the like, research and development for high-performance secondary batteries capable of repeatedly charging and discharging has been actively made.
Currently, nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, lithium secondary batteries, and the like are used as commercial secondary batteries. Among them, lithium secondary batteries have little to no memory effect in comparison with nickel-based secondary batteries, and thus lithium secondary batteries are gaining a lot of attention for their advantages of free charging/discharging, low self-discharging, and high energy density.
Meanwhile, with the steady exhaustion of carbon energy and increasing interest in the environment, the demand for hybrid vehicles and electric vehicles is gradually increasing all over the world including United States, Europe, Japan, and the Republic of Korea. Hybrid vehicles and electric vehicles are supplied with power for driving the vehicles from the charging/discharging energy of battery packs. Therefore, in comparison with vehicles powered by an engine alone, they have higher fuel efficiency and can eliminate or lessen the emission of pollutants, which adds to the appeal of hybrid vehicles and electric vehicles. Accordingly, research and development for vehicle batteries essential to hybrid vehicles and electric vehicles have intensified with gaining interest.
Today, one of the technologies gaining attention is an energy storage technology such as smart grid systems. The smart grid system is an intelligent power distribution system that aims to improve the power utilization efficiency through the interaction between power supply and consumption by applying the information and communication technology to the production, delivery, and consumption of energy. To implement such a smart grid system, one of the important elements is a battery pack configured to store power.
Similarly, batteries are being applied in various fields, particularly in the field of hybrid vehicles, electric vehicles, and smart grid systems recent trend, which requires batteries to have high capacity. To improve the capacity of a battery pack, consideration may be taken to increase the size of a respective battery pack. However, in this case, there are physical limitations in expanding the size of a battery pack and inconvenience in managing a battery system. Thus, it is common to connect a plurality of battery packs in parallel to construct a high-capacity battery system.
However, when a plurality of battery packs having different states of charge (SOCs) are connected in parallel, electric sparks may occur. In particular, in the case of widely used lithium secondary batteries, since they have a higher discharging current than other batteries, when battery packs having different SOCs are connected in parallel, battery cells or circuits included in the battery packs may be injured or damaged. Moreover, the occurrence of electric sparks may cause harm or damage to the safety of a user or installer connecting the battery packs.
Further, after connecting a plurality of battery packs in parallel, one or more battery packs may be additionally connected to improve the storage capacity or may replace a certain damaged battery pack. In this case, when the additional battery pack to be connected has different SOC from those of the battery packs already connected in parallel, electric sparks may occur, causing injure or damage to battery cells or circuits included in the battery packs as well as the safety of a user.